Sorption heat pumping technologies: Comparisons and challenges

Heat pumping devices which are operating on sorption effects comprise at least two times two categories, namely liquid or solid sorption cycles on the one hand, and open or closed cycles on the other hand. For the benefit of energy saving and the environment as well as for the further development of the technology it is important to be able to compare and evaluate these options in the context of the respective application. Some ideas to this end are shown in this paper.First the meaning of temperatures and humidity for the difference between open and closed systems is discussed, and there are a lot of similarities. Then some differences between solid and liquid sorption which are especially important for the question of minimum operating temperature and part load behavior are being reviewed, and we find that there is something to learn, mutually. Finally the consequences of solar fraction, auxiliary power consumption, and cogeneration efficiency are being highlighted, in order to check the perception of sorption systems to be environmentally benign. These consequences are important for all kinds of sorption cooling systems. It can be expected that there are significant improvements in the efficiency of power plants and compression cooling systems; consequently we find that sorption technology must improve its performance considerably also in order to stay competitive.